/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package org.apache.commons.collections4.multiset;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.util.Collection;

import java.util.Iterator;

import java.util.Set;

import java.util.function.Predicate;

import org.apache.commons.collections4.MultiSet;

import org.apache.commons.collections4.Unmodifiable;

import org.apache.commons.collections4.iterators.UnmodifiableIterator;

import org.apache.commons.collections4.set.UnmodifiableSet;

/**

 * Decorates another {@link MultiSet} to ensure it can't be altered.

 * <p>

 * Attempts to modify it will result in an UnsupportedOperationException.

 * </p>

 *

 * @param <E> the type held in the multiset

 * @since 4.1

 */

public final class UnmodifiableMultiSet<E>

        extends AbstractMultiSetDecorator<E> implements Unmodifiable {

    /** Serialization version */

    private static final long serialVersionUID = 20150611L;

    /**

     * Factory method to create an unmodifiable multiset.

     * <p>

     * If the multiset passed in is already unmodifiable, it is returned.

     *

     * @param <E>  the type of the elements in the multiset

     * @param multiset  the multiset to decorate, may not be null

     * @return an unmodifiable MultiSet

     * @throws NullPointerException if multiset is null

     */

    public static <E> MultiSet<E> unmodifiableMultiSet(final MultiSet<? extends E> multiset) {

        if (multiset instanceof Unmodifiable) {

            @SuppressWarnings("unchecked") // safe to upcast

            final MultiSet<E> tmpMultiSet = (MultiSet<E>) multiset;

            return tmpMultiSet;

        }

        return new UnmodifiableMultiSet<>(multiset);

    }

    //-----------------------------------------------------------------------

    /**

     * Constructor that wraps (not copies).

     *

     * @param multiset  the multiset to decorate, may not be null

     * @throws NullPointerException if multiset is null

     */

    @SuppressWarnings("unchecked") // safe to upcast

    private UnmodifiableMultiSet(final MultiSet<? extends E> multiset) {

        super((MultiSet<E>) multiset);

    }

    //-----------------------------------------------------------------------

    /**

     * Write the collection out using a custom routine.

     *

     * @param out  the output stream

     * @throws IOException if an error occurs while writing to the stream

     */

    private void writeObject(final ObjectOutputStream out) throws IOException {

        out.defaultWriteObject();

        out.writeObject(decorated());

    }

    /**

     * Read the collection in using a custom routine.

     *

     * @param in  the input stream

     * @throws IOException if an error occurs while reading from the stream

     * @throws ClassNotFoundException if an object read from the stream can not be loaded

     * @throws ClassCastException if deserialised object has wrong type

     */

    @SuppressWarnings("unchecked") // will throw CCE, see Javadoc

    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {

        in.defaultReadObject();

        setCollection((Collection<E>) in.readObject());

    }

    //-----------------------------------------------------------------------

    @Override

    public Iterator<E> iterator() {

        return UnmodifiableIterator.<E> unmodifiableIterator(decorated().iterator());

    }

    @Override

    public boolean add(final E object) {

        throw new UnsupportedOperationException();

    }

    @Override

    public boolean addAll(final Collection<? extends E> coll) {

        throw new UnsupportedOperationException();

    }

    @Override

    public void clear() {

        throw new UnsupportedOperationException();

    }

    @Override

    public boolean remove(final Object object) {

        throw new UnsupportedOperationException();

    }

    /**

     * @since 4.4

     */

    @Override

    public boolean removeIf(Predicate<? super E> filter) {

        throw new UnsupportedOperationException();

    }

    @Override

    public boolean removeAll(final Collection<?> coll) {

        throw new UnsupportedOperationException();

    }

    @Override

    public boolean retainAll(final Collection<?> coll) {

        throw new UnsupportedOperationException();

    }

    //-----------------------------------------------------------------------

    @Override

    public int setCount(final E object, final int count) {

        throw new UnsupportedOperationException();

    }

    @Override

    public int add(final E object, final int count) {

        throw new UnsupportedOperationException();

    }

    @Override

    public int remove(final Object object, final int count) {

        throw new UnsupportedOperationException();

    }

    @Override

    public Set<E> uniqueSet() {

        final Set<E> set = decorated().uniqueSet();

        return UnmodifiableSet.unmodifiableSet(set);

    }

    @Override

    public Set<MultiSet.Entry<E>> entrySet() {

        final Set<MultiSet.Entry<E>> set = decorated().entrySet();

        return UnmodifiableSet.unmodifiableSet(set);

    }

}